Method of making a laminated core



March 19, 1957 H. L. Fx-:RVERDA METHOD OF MAKING A LAMINTED CORE 2 sheets-sheet 1 Filed July 25, 1955 March 19, 1957 H. FERVERDA 2,786,006

METHOD OF' MAKING A LAMINATED\\ CORE Filed July 25, 1955 2 Sheets-Sheet 2 'y ASA vr/761g.

HOD OF MAKIN G A LANIVINATEDJCORE Harold L. Farmen For: wayne, 1nd assigner. to, General Electric Company, a` corpi,1i-ation of iblew'Ynjlcl Applicationlluly 25, 1955; SerialtNo..524,0.4 .i

17 Claims. (Cl. 154-80) This inyention relates toelectrial apparatus, and more particularly to a noyel method of making a 'l,ainitiatedeure'` member for use iny such apparatus.

Itis aA well-known fact that in electrical apparatus,` ot the typeincluding induction devices such as ,transformera and dynamoelectric machinery, such as motors', it necessary to provide a core member of magnetic material as apath for the magnetic uxes produced. These c ore members, particularly those intended for use in alternat-V ing current apparatus', have invariably been found to p rovide better performance when they are made up of a plurality'of thin superimposed laminations. 4Such a struc ture, however, presents certain problems as to assembly of the individual 'laminations and the maintenance thereof in a stack asa unitbecause presentl methods offasse'mblydo not proyide'the stack with the desired rrrel'ianicalV strength. lt -is most 4desirable to provide a methodfofY making a laminated core member wherein the lamina'- tions are secured together so that the stack has higheris further desirable to provide a methodtof making `a coe member wherein the insulationrbetween thecore merrlrb'er plurality of grid members 3, are `arranged. soas to define 2,786,006 PatentedA Mar.l 19, 195] 2 Figurerll is a diagram setting forth in sequencegthre `four basiclstepsofA the invention.

Referring now to Figures l and 4 of the drawings, the lirstfembodiment of the improved method will lbe deseriljedLl yTwo grid sections` 1 and 2, each consisting of a between them and area 4. The individual gridrnembers 3f: of each group are interconnected, as shown at 5`and6, and theA two sections are'connected together by a conductor 7. fconductor Sis electrically connected to one grid section 2'y and is adapted `to be connected to the lnegative, side of and the windings which are to beplacedthereon is foi'me'cllV in the same operationas the securing together offthe lamir nations. vIt is, of course, alsoa` requirement thatrnsuch` a method t be economicall andA simple.

`lIt is, therefore, an object of this invention to prov-ide `an improved method of making a 'laminatedcore .member whichV will inclu-de thedesirable features set forth abovew Further objects` and advantages of` this invention will become apparent and the;A invention willsbe 'bet'terfunder-V stood by reference to the iollowing..description and. the

accompanying drawings, andahe feature-slof novelty which characterize .this inventionfwill be pointed out` Withparf` ticularity in the claimsannexed to and forming a. pat'Lo-f this specification. t 1 A 111V its. broadest aspect, this invention provides `a fourstep method.v `ofmaking ,cores for ,electrical vapparatus".` i In` thelrst` step,` `grolmded individualvlaminations, arepassed throug'hgtanelectrostatic yfield and solid particlesoton-4 sulatingand `bonding resinjare introduced@ into thelfieldto coatthe-llaminations. VEach` lamination is thenheatedsoj as tomelt atrleast the outer .surface of theparticlesfcoating it.` The '-laminations lare then'l staclred` predetr?" m'ined-iheight' solas to forma lcore`,a,nd,in ther-last"step,y

areftheriheated either merely to melt there n Qff' the. .fh th to effect a 'modificationVf of the v"firststepI lof this inven hasl been shown, any type-of apparatus capable of'sprayaf source of direct current power so as to maintain the gridsections at a relatively high voltage. While various voltagesfmayA be used, it has been found that optimum resultsare obtained inthe range of 60,000 to 100,000 volts.

, A-majorityof the tests run by the inventor includedfa grid voltagev 'of 70,000 volts, and highly satisfactoryresults wereY obtained.4 The grid sectionsland 2 maybe each supported on a supporting member 9 with adequate insulation arranged between the supports 9 and v'the'grid sections 1 and 24 to preclude grounding of the grid sections. It will be clear to those familiar in the art that with Asuch anarrangement an electrostatic field maybe created in the area 4 for a purpose hereinafter described. A guide rail 21 is arranged to support a plurality of rolling members 11, eachof which is connected to a rodtlZ through apart 13 which maybe arranged to cause rod.12 to rotate in the direction shown by arrow 14 as roller 11' movesA to the right alongV rail 21. Each rod 12 has a hook member 15 formed at. the bottom thereof, and "supported on thehook as` partof the` stator of a dynamoele'ctric machine (not shown),'and it will be seen that slots 17-'have be'en provided for windingsto be placed in the core formed ofthe laminations 16. Rail 21, roller 11, Arod'12, and part 13 are all formed ofy conductive material, andthe rail 21 is connectedtto the positive side of the, source of direct Vcurrexit power by line 22 so that ineiect each of the 1aminations 17 is connected to the positive side ot'the power source. For safetys sake, rail 21 is preferably grounded (not shown), but it will be clear thatsuch grounding forms no part of the invention but is a standardprecaution.

A gun-type spray device 18 having a nozzlej `19,'and

connected to a source of compressed air (not, shown)- through a pipe 27,0 and to a source of finely divided mate-A rial (not shown) through` anQtherpipeZS, is arranged as, `shown so as to spray` the material throughitsi'nozzle in` adirection, generally parallel to the travelof thelaminations lthrough the electrostaticeld 4. It will, howeyer, be 4understood that while agua-type arrangement 18 inginelydiyided particles mayy be used to equal advntage., When the particles entera theelectrostatic field 4,

areattracted to the11aminations,.which represent the positive side, of the line, or the anode. Each lamination 1s .thus coated with an amount of material which depends primarily on the amount being sprayed by device 1S, the

strchgth of therelectrostatic eldas determined by. the

vgltase' zapplied between lines .sand 22, ,the speed at which theY:laminatio'ns `are movedalong-track l21 throughthe` y held 4,1and the posit ion of thelaminations as .they pass through Vthe tiel-d. 4The materialmsprayed through` the dej. (ice4 1 8; is .-a resin, solid at thetemperatures atwhich the 4spraying operation 1s performed-,and at whichthe lrrishedelectrical core will be utilized, land having the desiredinsulating and `bonding qualities, which hasbeendivided into relatively iineparticles. It has 'been`discovered that particlesV which will pass through a60 mesh screenrareyof Vsmall enough `size and sufficiently economicalato be commercially desirable. However, itwillfbe understood that largerparticles may beuscdon occasion,

and that the upper size of the particles is determined primarily by their weight since at a certain size they will start to fall to the ground rather than remain in suspension in the electrostatic field. The weight, in turn, depends upon theV particular material used. The same in general is true as to the lower limitation on the -size of the particles, since the particles may be divided as iinely as desired and will still coat the laminations properly. However, at a certain size the danger of an explosionmay become a material factor and it will therefore be understood that it is desirable not to reduce the particles to such a size.

It is necessary that the material used 'be solid. at the temperature at which the iirst step of the process` is conducted since otherwise the material will tend to -bead at the -bottom of each lamination, and, more important, will y make the laminations exceedingly'dicultto handle sub sequently. One such type of material,which also has the desired features of insulation, bonding, and melting at a relatively high temperature, is found in the epoxide resins. There are several commercially available resins from this group which include 'all the desired features.

However, the process is not limited to resin particles from by sufficient heating they will remain solid, no matterwhat temperatures they are subsequently subjected to,

until they are destroyed. The chlorinated polyphenyl resins andthe shellac, on the otherY hand, are thermoplastic, i. e., they will always soften when heated to a predeterminedl temperature. Y While the broad concept of the process is independent of which type of resin is used,- it will be recognized that ea-ch type has certain advantages Thus, thermo- Y ysetting materials can -be used regardless of the temperaover the other when used in the process.

ture at which the electrical core is used, up to the temperature at which the material is destroyed; on the other hand, while thermoplastic materials must be selected So that the-melting temperature is well above that at whichY the electrical core will be used, the manufacturing process maybe simpler since it is not necessary to cure thematerial -by application of heat for a predetermined time, but onlyjto supply enough heat to melt it.

vIt will bereealled that'the rods 12 are caused to rotate as they pass through the electrostatic tiel-d'4. However, while this will provide a particularly good coating on; each laminationV inr combination with the particular position of th'espr'aying apparatus (as shown in Figure l), it ist to be understoodrth'at the vprocess is not limited to the combinationY of these particular factors. -The spraying apparatus may be arranged 'as shown without rotation of the rods 12 and will provide results which, although not asgood,are yet satisfactory. Y Y

After the laminations have been coated as described above,'they are exposed to'- heat so Yas to cause at least partial melting of the outer surface of the particles and arethen Iallowed to cool so that the resin forms a sub- `stantiallyfsolid coating-oneach lamination. f While dif-- lferent temperatures in .combination with'diierent periods of.` time mayfb'e used, Vand therefore there is nothingv criticalfabout that particular feature, it has `been found that raising the ambient temperature of the laminations" 70 provide'satisfa'ctory melting of the outer surface of the to approximately 100 C. for about fteen seconds will particles in at least ther epoxide resins set forth as examples above and for some membersV of the chlorinated polyphenyl resin group. However, for different resins the temperature .and time will vary, and -the import-antVN stance, with laminations such as those shown in Figure l,

a rod provided with alignment guides (not shown) Ymay be provided and the laminations stacked on the rod until If desired, pressure may be aV proper height is reached. applied Iso as to insure proper alignment and close con- .tact of the laminations. However, experimentation has 4also shown that no pressure at all will still provide a satisfactory core.

For the fourth step, the laminations may be maintained under the same pressure as for the previous step,

,- or, if so desired, other pressures, or even no pressure, may

' be provided.

190 C. for about one and a half hours.

In the caseV of thermosetting resins, they are then heated so that the resin is cured and yfuses into a solid unmeltable mass. This may be etected, in connection with the epoxide resins mentioned, lby baking at Again, however, the temperature and time may be varied for any one particular type of resin, and both will differ when different types of resins are used. The important thing with thermosetting resins is that suicient heat lbe applied to the stacked laminations to cure the resin. In the case of thermoplastic resins, they are heated so that the resin is melted; when the resin cools, the laminations are then lbonded together yby a material which, at the temperatures to be encountered during use, is unmeltable. There are Hmany thermoplastic insulating and bonding materials,

withmelting points far above the norm-al temperatures reached by electrical equipment during use, which may be selected. Y v

Referring now to Figure 2 of the drawings, the principal difference from the arrangement of Figure l lies in the factV that the spraying gun 18 has been moved so that its nozzle 19 sprays the particles of resin into the field 4 at approximately right angles, i. e., perpendicular, to the direction oftravel of the lamination 17 through the eld.

. With this arrangement, it is not necessary that the laminations be rotated as they pass through the eld in order to obtain optimum results; instead, best results are obtained when the laminations are so arranged on the hooks that they lie in a plane which is substantially perpendiew lar to the direction in which the particles are sprayed into the field. Again, however, it will be understood that while the best results are obtained with the laminations precluded from rotation and arranged as set forth above, satisfactory results may be obtained with the laminations L in any position as they pass through the field 4.

4, both of the devices spraying material at right angles to the direction of movement of the laminations. It has been discovered that, when two gunsor spraying `devices are provided in this arrangement, a pluralityof laminations maybe arranged on each rod 12 with excellent results. While it is possible to secure 7.a plurality; of laminations `on each rod 12 in the embodiments of Figures 1 and ,2,v if suicient hooks 1S are provided, the result is notas satisfactory as where a singleVV lamination is susp'ended from each rod. However, in the embodiment of Figure 3, the provision ofthe two guns with one on veach Vside of the field provides excellent coating of all ,the laminations.

1 It will be seen from the foregoing that this invention. provides a method of making cores for electrical appa ratus which is novel and economical. Furthermore, the

a;stregone? insul tw.. Dfhat windinssmaybaappliept withmit nu need oradditional insulation'.

While this`` invention' hasjbeen: explainedfzhy describing particularembodiments tluereof, it will'I be apparent that' haut improvements and modifications maybe. made wit departing` from the scope of tle inventinlas, dned in.

the 'appended claims. t

WhatI, claim as-newj andv desire to.secure by Letters Patent; of. thaUnitedStatesf isa 1. A'. method of making cores. for:

2.` A method of making cores-fori electrical-,appalatus. comprisingy the steps of passing. individual laminations'.

connected to the positive side of a source. oil direct; cur.,-v rent;y p'ower through an electrostatic iieldand; introducing solidD particles of thermosetting insulatingg resin'` intothe eid in a direction substantially parallel to thelline-.of`

movement of the laminations thereby tocoat-l said laminations, heating each lamination so as to. meltlthe: parR ticles together without curing the resin, coolingthe-lami-k nation sothat` the resin forms a solidlf coating, stacking said-laminations to a predetermined height; to formv a core, and heating the stacked laminations'` to meltand curel said resin.

3. A method of making cores for electrical apparatus comprising the steps of passing individual laminationsj connected to the positive side o fa s ource of direct cui@ rent power through an electrostatic ield andlintroducing solid` particles ofthermosettinginsulating `resin into the" field, thereby to coat said laminations, said' laminations,

being rotated as they p ass through Ytheiield, heatingY 1each lamination so as to nielt the particles togetherj'without curing the resin, cooling the lamination sothat thej resin forms a solid coating, stacking said laminations to a predetermined height to forma core and,` heating the stacked laminations to` melt and cure, spraidariesin.

4. A methodk of making core for electrical apparatus comprisingv lthe steps ofv passing individual laminations connected to thepositiveside of a source fof direct current power through an electrostaticiield andintroducing-solid particles of a thermosetting insulating resin into the eld thereby to coat said laminations, heating each lamination so as to melt the particles together without curing the resin, cooling the lamination so that Ithe resin forms a solid coating, stacking said laminations to a predetermined height to form a core and heating the stacked laminations to melt and cure said resin.

5. A method of making cores for electrical apparatus comprising the steps of passing individual laminations connected Ito the positive side of a source of direct current power through an electrostatic eld and introducing solid particles of a thermosetting insulating resin of the epoxide group into the eld thereby to coat said laminations, said laminations being rotated as they pass through the field, said resin being introduced into Ithe iield in a direction opposite to and parallel with the line of motion of said laminations, heating each lamination so yas to melt the particles together without curing the resin, cooling the lamination so that the resin forms a solid coating, stacking said laminations to a predetermined height to form a core, and heating the stacked laminations to melt and cure said resin.

6. A method of making cores for electrical apparatus comprising the steps of passing individual laminations ltrieal'apnaatus comprising the. Steps- Qi ass'ng. ndividuahlamintiml; o connected to the. positiveside. of. a.,s,o1l1rceofi directeur-1y between two sections of a grid rnaintained; at 60,0() 0-V to, 100,000 volts direct; current; the Vgrid being' connected to? theinegativesideof the directeur-rent power source and" thelaminationsbeingI connected to the positive, side thereof; introducing particles otra s olid;thermosetting insulat-i ing `resin of the epoxide type between the^` gridwsectionsj thereby to coat said laminations, heating each,` lamination to approximately C. for 'approXinatelyglSseconds; stacking; saidlaminations to a predetermined heighttoV form a`" core, and heating the stacked i laminations atf ap-A proximately ",a` 'Cl for approximatelyoneand;'afhalfn hours toineltandjcure saidresin, i ,v 7 A" 'niet-ha?. Qf matins Cores fOr-@leerikapiaras comprising the' steps'. of" passing individuallaminations connectedwto flic-positive'sideL of a' source of' direct ,current`` power through an 'electrostatic iieldii-and introducing'solid! particles of athermoplastic'insulatingresin intothe iiell; thereby; to coat said" la'niinatioiiisg,` heating each-lamination, so as to smelt theparticles together'cooling the lamination so-that 'the resinformsa solid coating, stackingsaid'lamii.

nationsto a predetermined height to form a core, andr heatingthe sta'ckedlaminations t'o'melt Vsaid resin thereby to bond said laminations together.,

8. vA rnethodlofA makingcores for electrical apparatus comprising the steps of passing individual laminations connected to :the positive sidefofl a sourceof direct `current power through an electrostatic held and introducingsolid` particles of; af Athermoplastic o insulating resin into `the field; thereby"y to coathsaid` laminations, said laminations being v causedto Yrot-ate as they are, passed, through the field, thel resin being introduced into the field in a direction-*substantially parallelto the line of` movement of saidilaminations, 4heating each lamination so as to melt the particles together, cooling .the lamination so that the resiniformn a solid coating; stacking said` laminations` to a predeter mined height to f orm -a core, and heating the stacked laminationslto melt said resin therebyto bond said lamina- .tions together. v Y i f 49. A method of making cores for electrical apparatus comprising the steps off passing individual laminations connected to the positive side of a source of direct current power through an electrostatic field `and introducing solid particles of insulating and bonding resin into the field` at substantially right angles totherdirection of movement of l saidlaminations thereby to coat said 1aminations,heating eachlamination so as to melt the particles together,- cool# ingV the lamination so that the resin forms a solid coating, stacking said laminations `to' a predetermined` height toform a core, and; heating` the stacked laminations toy melt.` said/resin thereby to bondV said laminations together.

l0. A method of making coresfor electricalapparatusv comprising the steps of passing individual laminations connected to the positive side of a source of direct current power through an electrostatic field and introducing solid particles of thermosetting insulating resin into the field at substantially right angles to the line of motion of said laminations thereby to coat said laminations, said laminations being maintained in a plane at substantially right angles to the direction in which said resin is introduced into the iield, heating each lamination so as to melt the particles together without curing the resin, cooling the lamination so that the resin forms a solid coating, stacking said laminations Ito a predetermined height .to form a core, and heating the stacked laminations to melt and cure said resm.

1l. A method of making cores for electrical apparatus comprising the steps of passing individual laminations between two sections of a grid maintained at 60,000 to 100,000 volts direct current, the grid being connected to the negative side of the source of direct current power and the laminations being connected to the positive side thereof, introducing between the grid sections solid particles of thermosetting insulating resin of the epoxide type in order to coat said laminations, the material being introduced approximately at right angles to the line of motion of said laminations, said laminations being main arcanos.

proximately-190 C. for approximately oneand a halfV hours tpomelt and cure said resin. jj .y

121.A A meth'od of making cores for electrical apparatus comprising the steps of passingV individual laminations conneeted tothe positive side of a sourceof direct current power through an electrostatic.iiell` and` introducing solid panticles ofa thermoplastic .insulating resin into the iieldl atepproximately right angles tothe direction of movementofsaidlaminations to coatsaidlaminations, said laminationsfbeing maintained'at substantially right angles ltofthefdrirection of introduction ofthe particles into the field,V heating each laminationso'as to melt the particles together, cooling the lamination so that the resin forms a solid coating, stacking said laminations toa predetermined height to form a core, and heating thestacked laminations to melt said resin thereby to bond said laminations together.

13. A method of making cores for electrical apparatus comprising Ythe steps of passing individual laminations connected to the positive side of a source of direct current power through an electrostatic field and introducing solid particles of insulating and bonding resin into the cld from each side of said laminations at approximately right angles to the direction of movement thereof so as to coat saidlaminations, heating each lamination so as -to melt the particles together, cooling the lamination so that the resin forms a solid coating, stacking said laminations to a predetermined height to form a core, and heating the stacked 'laminations to melt said resin thereby to bond said laminations together. n e

l14. A method of making cores for electrical apparatus comprising the steps of passing individual laminations connected lto the positive side of a source of direct current power through an` electrostatic eld and introducing solid particles of thermosetting insulating resin into the eld from both sides*V of said laminations at approximately right angles to the direction of travel thereof to coat said laminations, saidlaminations being maintained at substantially -rightfangles to the direction of introduction ofV the particles into the eld, heating each lamination so -as to melt the particles together without curing the resin, cooling thelamination so that the resin forms a solidl coating; stacking said laminations to a predetermined comprisingthe steps, of passing individual laminations between two'sections of a gridmaintained at 60,000 tof 100,000 volts direct current, the grid being connected tothe'negative side ofthe source of direct current power and the laminations -being connectedto the'positive side thereof,l introducingsolidlparticles offthermos'etting in-Y sulating resin'of the'epo'xide type into Ithe field from both sides of said'laminations at approximately right angles to the directionof 'movement thereof thereby to coat said laminations, ,said laminations being maintained at substan' tially right anglesVv tothe direction of introduction'of the particles into thepjeld, heating each lamination at approx' imately C. for approximately l5 seconds so as to melt atleast the outer surfaces of the particles, vstacking said laminations to a'predeterminedrheight to form a core, and` heating thel stacked laminationsqat approximately C. for approximately one and a half hours to melt and cure saidresin.Y Hf Y' l16.V A method of making cores for kelectrical apparatus comprising the 4steps of' passing individual laminations connected to the positive side of a source of direct current power through anV electrostatic field andv introducing solid particles of a thermoplastic insulating resin into the field from both sides of saidlaminations at approximately right angles to the direction of movement thereof thereby to coat said laminations, said laminations being maintained at approximately right angles .to the direction of introduction of theV particles into the tield, heating each lamination so as to melt the particles together, cooling the lamination so that the resin forms a solid coating, stacking said laminations to a predetermined height to form a core, and heating the stacked laminations to melt said resin thereby to bond said laminations together.

1 7.-A method of making cores for electrical apparatus comprising the steps'ofpassing individual laminations connected to the positive side of a source ofdirect current power through an electrostatic eld and introducing solid particles of thermosetting insulating resin into the field from veach side of said laminations at -approximately right angles to the direction of movement thereof sopas to coat said laminations, heating each lamination so as to melt the particles together without curing the resin,'cool ing thelamination so that the resin forms a solid coating, stacking Asaid laminations to a predetermined height to form a core', and heating the stacked laminations to melt and cure said resin.

vReferences Cited in the tile of this patent t UNITED STATES PATENTS 2,275,989 Perry Mar. 10, 1942 2,421,787 l Helmuth4 June 10, 1947 2,483,024 lRoters Sept. 27, 1949 

1. A METHOD OF MAKING CORES FOR ELECTRICAL APPARATUS COMPRISING THE STEPS OF PASSING INDIVIDUAL LAMINATIONS CONNECTED TO THE POSITIVE SIDE OF A SOURCE OF DIRECT CURTENT POWER THROUGH AN ELECTOSTATIC FIELD AND INTRODUCING SOLID PARTICLES OF INSULATING AND BONDING RESIN INTO THE FIELD THEREBY TO COAT SAID LAMINATIONS, HEATING EACH LAMINATION SO AS TO MELT THE PARTICLES TOGETHER, COOLING THE LAMINATION SO THAT THE RESIN FORMS A SOLID COATING, STACKING SAID LAMINATIONS TO A PREDETERMINED HEIGHT TO FORM A CORE, AND HEATING THE STACKED LAMINATIONS TO REMELT SAID RESIN THEREBY TO BOND SAID LAMINATIONS TOGETHER. 